1. Field of the Invention
The present invention generally relates to computer networks, and more particularly, to a system and method for coupling signals to a power line network.
2. Discussion of the Related Art
LANs are computer networks operating over a small area such as a single department in a company. Most LANs serve to transport data between personal computers and workstations and file servers. In general, the devices on a LAN must follow certain rules of operation to communicate effectively. These rules of operation are known as protocols. A variety of different LAN protocols are available. For example, the IEEE 802.3 standard deals with a network architecture and protocol termed Ethernet. Stations in an Ethernet network may be connected through interfaces to a coaxial cable, twisted pair wire or fiber optics. A major disadvantage associated with Ethernet technology is the cost of routing a transmission medium between each proposed station on the LAN.
The dramatic growth of Internet applications has created the need for small office, home office, and remote locations with multiple personal computers (PCs) to share high speed interfaces with the Internet. In addition, business and home office configurations have a need to share files and peripheral devices, such as printers, among several PCs. A variety of techniques to interconnect various closely located PCs, peripherals, and xe2x80x9cInternet compatible appliancesxe2x80x9d have been proposed including: radio-frequency (RF), infrared, existing phone lines, power lines, and traditional cabling methods. Each of the alternative infrastructure configurations has advantages and disadvantages for the end user.
RF transceivers may provide a wireless mechanism to interconnect various PCs and related peripherals inside a home or office. BLUETOOTH(trademark)xe2x80x94is an example of a low-power RF implementation. RF transceiver infrastructures eliminate most of the cabling from the LAN and provide limited location independence for their users. In order to effectively transfer data, the data transmissions must be broadcast with sufficient power to enable reception and accurate demodulation of the intended data signal at the receiving device. As a result, RF systems are subject to xe2x80x9ceavesdroppersxe2x80x9d that might intercept the radiated data signals. Furthermore, RF LAN infrastructure systems may require Federal Communications Commission (FCC) licenses to operate equipment at certain frequencies, adding to the installation and operating expense of the system. RF systems designed to operate in unlicensed frequency bands assume a potential risk of interference from other users. In order to achieve practical data rates and reasonable antenna sizes using RF technology without the added expense of procuring broadcast licenses, typical implementations operate between 2 to 3 GHz in the unlicensed band of frequencies. This frequency range suffers from significant degradation due to path loss in environments with significant water vapor. In short, RF LAN infrastructures suffer from low security and the risk of RF interference from operators of like equipment. In addition, RF LAN implementations may suffer from interference from microwave ovens and significant signal power loss in damp environments.
BLUETOOTH(trademark) is a low-power RF technology designed to operate in the 2.4 GHz ISM band. BLUETOOTH(trademark) is designed to operate over a distance of 10 meters with the goal of interfacing various local devices without cables. Ideally, BLUETOOTH(trademark) compatible devices could connect via the low-power RF link to enable a laptop computer to access an Email account via a cellular phone. The link is established without traditional cabling between the cellular phone and the laptop computer, assuming both devices are equipped with the BLUETOOTH(trademark) RF technology and are within transmission range of each other. BLUETOOTH(trademark) suffers from security issues like other RF technologies. Security issues are not as severe for BLUETOOTH(trademark) due to its lower transmitted power. On the other hand, lower transmitted power results in a shorter effective range of operation.
Infrared (IR) communications were popularized by the television remote control and have since penetrated a host of other home electronic device, personal data assistant (PDA), and laptop computer markets. Current technology uses IR light emitting diodes (LEDs) to emit sufficient optical energy to communicate data between devices within line of sight of one another. As such, IR communications are limited to a particular room as the frequencies do not penetrate solid objects. Data rates as high as 16 Mbps are expected to soon be a reality as IR communications standardization groups drive the technology.
Telephone lines are a common fixture in most every US home. In addition, most PCs are equipped with telephone modem technology and are usually connected to a telephone line servicing the home via a jack and a patch cord. Modem manufacturers have interconnected PCs through the use of various modulation schemes at high frequencies to avoid interference from POTS and standard data modem communications. A home networking consortium technology (Home PNA) was formed to advance phone line networking. The consortium has developed a series of standards defining protocols. However, unterminated stubs, crosstalk, poor frequency response, noise, ingress, and egress are issues that have hindered a successful market deployment of phone line based LAN technology. Another shortcoming of the technology is the throughput capability of the system. The current Home PNA standard supports a throughput of 1 Mbps. Contrast the expected transfer rate of 16 Mbps for wireless IR connected systems. In addition to the aforementioned shortcomings of phone line based LAN technology, this technology may have difficulty traversing from home networks into the typical office environment as a significant number of offices are wired in a star topology to support private branch exchange (PBX) telephone systems.
Power Line networks are networks established across power lines, such as wiring within the structure of a home or small office. In such networks, data signals are carried (e.g. modulated) over the 60 Hz power signals that are carried on those lines. As is known, certain difficulties and issues exist in these systems. First, a power line is an inherently noisy medium for data transmission, particularly high frequency data transmissions. Another issue that arises in implementing power line networks relates to data security and loss of transmission bandwidth with others on the same side of the power line transformer. One example of a system and method for communicating data over power line, or in-wall, wiring is disclosed in U.S. Pat. No. 6,014,386, which is incorporated herein by reference.
There are various problems or difficulties in implementing power line networks. One problem or shortcoming that is present in prior art systems is the direct coupling of circuit components to the power line. When processing or component circuitry is directly coupled to power lines, then power surges, spikes, and other transients that occur on power lines are directly coupled to the processing or component circuitry. This leads to premature component failure and destruction. This shortcoming is avoided in systems that use xe2x80x9cwall wartsxe2x80x9d to provide the gateway to the power line network. However, such systems generally have an unnecessary duplication of many circuit components. For example, the wall warts include transformers, filters, transient suppression circuitry, and other circuit components that are often present in the switching power supply of computer.
Accordingly, there is a desire for a system and method for providing power line networking that overcomes the problems and shortcomings of the prior art systems.
Certain objects, advantages and novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the objects and advantages of the present invention, the present invention is directed to a computer system having novel circuitry for coupling peripheral cards to a power line network. In this regard, the computer includes a switching power supply having coupling circuitry for coupling an electrical signal with a power line, a filter circuit electrically connected to the coupling means for receiving an electrical signal from the coupling means and filtering the received signal, and an amplifier circuit electrically connected to the filter circuit for amplifying the filtered signal. The computer system also includes at least one peripheral circuit (e.g., PC card). An infrared transmitter is coupled to the amplifier circuit for transmitting an infrared signal. The computer also preferably includes a diffuser disposed to receive the infrared signal output from the infrared transmitter. The diffuser is operative to scatter the infrared signal in multiple directions so that it may be readily received by various infrared receivers disposed in various locations. Finally, the computer includes an infrared receiver coupled to the peripheral circuit for receiving the scattered infrared signal.
In accordance with another embodiment of the invention, a power line adapter is provided for communicating signals between a power line and a computer. The power line adapter includes a first connector for connection with a power line and a second connector for connection with a computer. The adapter further includes coupling circuitry for coupling an electrical signal with the power line. The adapter further includes means for communicating the electrical signal coupled with the power line to and from a remote location.
In accordance with another aspect of the invention, a method is provided for coupling a power line with a peripheral card in computer system. The method operates by coupling an electrical signal, within a switching power supply, with the power line, transmitting the electrical signal through an infrared transmitter disposed at the on the switching power supply, diffusing the signal transmitted from the infrared transmitter, and receiving the diffused signal through an infrared receiver disposed on a peripheral card.